// MIT License

// Copyright (c) 2019 Erin Catto

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#ifndef B2_SHAPE_H
#define B2_SHAPE_H

#include "b2_api.h"
#include "b2_math.h"
#include "b2_collision.h"

class b2BlockAllocator;

/// This holds the mass data computed for a shape.
struct B2_API b2MassData
{
  /// The mass of the shape, usually in kilograms.
  float mass;

  /// The position of the shape's centroid relative to the shape's origin.
  b2Vec2 center;

  /// The rotational inertia of the shape about the local origin.
  float I;
};

/// A shape is used for collision detection. You can create a shape however you like.
/// Shapes used for simulation in b2World are created automatically when a b2Fixture
/// is created. Shapes may encapsulate a one or more child shapes.
class B2_API b2Shape
{
public:

  enum Type
  {
    e_circle = 0,
    e_edge = 1,
    e_polygon = 2,
    e_chain = 3,
    e_typeCount = 4
  };

  virtual ~b2Shape() {}

  /// Clone the concrete shape using the provided allocator.
  virtual b2Shape* Clone(b2BlockAllocator* allocator) const = 0;

  /// Get the type of this shape. You can use this to down cast to the concrete shape.
  /// @return the shape type.
  Type GetType() const;
  
  /// Test a point for containment in this shape. This only works for convex shapes.
  /// @param xf the shape world transform.
  /// @param p a point in world coordinates.
  virtual bool TestPoint(const b2Transform& xf, const b2Vec2& p) const = 0;

  /// Compute the distance from the current shape to the specified point. This only works for convex shapes.
  /// @param xf the shape world transform.
  /// @param p a point in world coordinates.
  /// @param distance returns the distance from the current shape.
  /// @param normal returns the direction in which the distance increases.
  virtual void ComputeDistance(const b2Transform& xf, const b2Vec2& p, float32* distance, b2Vec2* normal) const= 0;

  /// Cast a ray against a child shape.
  /// @param output the ray-cast results.
  /// @param input the ray-cast input parameters.
  /// @param transform the transform to be applied to the shape.
  /// @param childIndex the child shape index
  virtual bool RayCast(b2RayCastOutput* output, const b2RayCastInput& input,
            const b2Transform& transform) const = 0;

  /// Given a transform, compute the associated axis aligned bounding box for a child shape.
  /// @param aabb returns the axis aligned box.
  /// @param xf the world transform of the shape.
  /// @param childIndex the child shape
  virtual void ComputeAABB(b2AABB* aabb, const b2Transform& xf) const = 0;

  /// Compute the mass properties of this shape using its dimensions and density.
  /// The inertia tensor is computed about the local origin.
  /// @param massData returns the mass data for this shape.
  /// @param density the density in kilograms per meter squared.
  virtual void ComputeMass(b2MassData* massData, float density) const = 0;

  Type m_type;

  /// Radius of a shape. For polygonal shapes this must be b2_polygonRadius. There is no support for
  /// making rounded polygons.
  float m_radius;
};

inline b2Shape::Type b2Shape::GetType() const
{
  return m_type;
}

#endif
